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There is a Fungus Among Us (or at least among them)

I gave a talk the other night to the Raleigh Chapter of the Carolina’s Nature Photographers Association. They were a great group and seemed to enjoy my topic about macro photography. One story, in particular, raised a few eyebrows. It was about something I see going on right now out in the patch of goldenrod under the power line.

Soldier Beetle feeding on Goldenrod (click photos to enlarge)

The patch is abuzz with all sorts of insects feeding on the copious quantities of nectar and pollen to be found in the golden buffet. Among the many foragers are a group of common beetles known as Soldier Beetles (also known as Leatherwings), Chauliognathussp. They are busy feeding on pollen and mating and are frequent visitors to various species of goldenrod and boneset that occur on the power line. In the past couple of weeks I have noticed something strange happening amongst their ranks…

Dead Soldier Beetle on goldenrod

The beetles are hanging down underneath the flowers with their wings askew in what looks like some strange circus acrobat position, but with a decidedly non-circus look about them. They look and are, in fact, dead.

Soldier Beetle on boneset

And there are lots of them this year – a large die-off of these beetles in what is certainly one of nature’s more bizarre local stories.

Group of dead Soldier Beetles

A close look at the dead bug shows a fuzzy white coating coming out between the segments of the lifeless body. The culprit is one of a group of arthropod pathogenic fungi. There are apparently many species of these insidious fungi, and many are host specific. The general life cycle is that an insect picks up a spore of the fungus on its exoskeleton while moving about in its environment. The spore then germinates and penetrates into the exoskeleton of its host via mechanical pressure and the production of enzymes which help dissolve an entry hole. Once inside, the fungus grows and divides. There is often an attack on the nervous system of the host which causes a change in its behavior near the time of death. In the case of these Soldier Beetles, they clamp onto the vegetation with their mandibles. In one study in Arkansas, an estimated 20% of the beetles surveyed in a field were infected by the fungus. And in an interesting finding, the researchers observed “by an unknown mechanism the fungus causes the dead beetles to raise their elytra between 2400 and 0700 hours during the night”. The position of the raised wings presumably provides a more efficient means for the fungus to disperse its spores from the dead insect.

This is a bit late, but I found this same thing this year. Dozens of Soldier Beetles are clamping down on Queen Anne’s lace and dying. I took some pics (using a doublet pressed against my
Ipod) and started researching, but it took me a while to find this. Thanks for posting!